The present invention relates to boron- and/or aluminum-containing, silicon-containing mixtures and hybrid materials and coatings produced therefrom.
German Patent Applications DE-A 19,603,242 and DE-A 19,603,241 and PCT Application WO 94/06807 describe numerous organosilanes from which inorganic-organic hybrid materials can be prepared via a sol-gel process. These materials can be employed, for example, for coating surfaces. The coatings, which can be cured at room temperature, are distinguished, for example, by a high transparency, good resistance to solvents, and good resistance to mechanical wear, with simultaneous elasticity. As a disadvantage, the mixtures described therein are not suitable for coating transparent substrates, such as plastic or glass, if these substrates are exposed to extreme mechanical stresses. For these materials, the wear resistance requirements are, of course, particularly high, since even the slightest damage impairs at least the visual impression. It was, therefore, desirable to improve the surface hardness of sol-gel coatings, in particular those based on the above-mentioned polyfunctional organosilanes, in order to be able to employ them in the coating of preferably transparent substrates.
The object of the present invention was, therefore, to provide mixtures based on monomeric polyfunctional organosilanes from which it is possible to produce coatings and for which the resistance to mechanical wear is significantly improved compared with the known systems and which are suitable for coating transparent substrates.
Surprisingly, it has now been found that the object can be achieved with the mixtures according to the invention of monomeric polyfunctional organosilanes and certain boron- and/or aluminum-containing compounds.
The present invention, therefore, relates to mixtures comprising
(A) at least one linear, branched, or cyclic monomeric organosilane having at least two silicon atoms with hydrolyzable and/or condensation-crosslinking groups, wherein the silicon atoms are bonded to one another through at least one carbon atom in a linking unit, and
(B) at least one boron- and/or aluminum-containing compound having the formula (I)
RxM(ORxe2x80x2)3-xxe2x80x83xe2x80x83(I)
xe2x80x83wherein
M is Al or B,
x is 0, 1, or 2,
R is C1-C6-alkyl, C6-C12-aryl, or (O)1/2, with the proviso that if R is (O)1/2, then the compound of the formula (I) is a chain when x is 1 and a cyclic or cage-form compound when x is 2, and
each Rxe2x80x2 is independently H, C1-C10-alkyl, or C6-C12-aryl.
The invention further relates to hybrid materials prepared from such mixtures and to coatings produced therefrom.